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  #1  
Old 02-25-2012, 09:33 PM
Tau Zero's Avatar
Tau Zero Tau Zero is offline
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Exclamation New Design -- Centuri 1972 "0810" 1.30X

Wandering through the Centuri 1972 catalog, I came across three "non-kitted" designs on page 54. I had worked them up in the original sizes back in September 2005.

Since we all know I *can't* leave well enough alone , and now that the Semroc Nose Cone Designer is up and running, I took a crack at upscaling the middle ST-8 and -10 design slightly.

I noticed that ST-8 and -10 upscale by 1.29X to ST-11 and 13. The slightly bigger version turned in some pretty good performances. So while I don't have an official name for it, I call it the "0810" design, referring to the original body tube sizes.

I'll post the nose cone and reducer/transition files separately.

http://forums.rocketshoppe.com/show...893&postcount=2

http://forums.rocketshoppe.com/show...897&postcount=3

.
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Jay Goemmer
"Centuri Guy"/"Tau Zero"
YORF Member 28
Semroc SAM #0029
NAR 86131


"I think about organizing things all the time. Never seems to happen. I find something that piques my interest and I'm off on a quest. Or a Centuri. "

--Bill Eichelberger, 02/22/2022


“Centuri fret buzz in an updated form.”
Bill “Wallyum” Eichelberger re: Estes Flutter-By
03 Sept 2014

Last edited by CenturiGuy : 02-25-2012 at 10:04 PM.
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  #2  
Old 02-26-2012, 02:00 AM
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mwtoelle mwtoelle is offline
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You seem to be missing a fin. The thing that I remember about most Centuri designs is the most of them had four fins instead of the three fins that appear in your Rocksim pictures.
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Mike Toelle

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  #3  
Old 02-26-2012, 06:33 AM
jetlag jetlag is offline
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I think the picture in the catalog shows a 3-finned rocket.

Allen
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  #4  
Old 02-26-2012, 07:51 PM
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Tau Zero Tau Zero is offline
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Talking So, how many fins ARE there?

Quote:
Originally Posted by mwtoelle
You seem to be missing a fin. The thing that I remember about most Centuri designs is the most of them had four fins instead of the three fins that appear in your Rocksim pictures.
Mike,

That's an interesting point. The design on the left shows 3 fins (maybe implying 4 of them), but for some reason I interpreted the other two designs as having 3 fins. This is obviously a case of Your Mileage May Vary.

Good catch.


Quote:
Originally Posted by jetlag
I think the picture in the catalog shows a 3-finned rocket.
Mike and Allen,

RockSim gives good results with only 3 fins, but when I upscaled Design #1 to ST-10, 4 fins weren't enough to slow down the deployment speeds. 5 fins might have done it, though.

(chuckling) That's why this hobby is so much fun! You can do things your own way, and learn from other people who do it differently.


Cheers,
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Jay Goemmer
"Centuri Guy"/"Tau Zero"
YORF Member 28
Semroc SAM #0029
NAR 86131


"I think about organizing things all the time. Never seems to happen. I find something that piques my interest and I'm off on a quest. Or a Centuri. "

--Bill Eichelberger, 02/22/2022


“Centuri fret buzz in an updated form.”
Bill “Wallyum” Eichelberger re: Estes Flutter-By
03 Sept 2014
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  #5  
Old 02-26-2012, 10:04 PM
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Carl@Semroc Carl@Semroc is offline
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I don't see but two fins!
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  #6  
Old 02-26-2012, 10:11 PM
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Tau Zero Tau Zero is offline
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Quote:
Originally Posted by Carl@Semroc
I don't see but two fins!
Yes, but *other* people are using their imaginations... maybe more than they *should* be!

(...He said, pointing his finger at himself... )
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Jay Goemmer
"Centuri Guy"/"Tau Zero"
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NAR 86131


"I think about organizing things all the time. Never seems to happen. I find something that piques my interest and I'm off on a quest. Or a Centuri. "

--Bill Eichelberger, 02/22/2022


“Centuri fret buzz in an updated form.”
Bill “Wallyum” Eichelberger re: Estes Flutter-By
03 Sept 2014
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  #7  
Old 02-26-2012, 10:46 PM
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ScaleNut ScaleNut is offline
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I wonder about the balsa grain on the third model ... is there a benefit to running it that way ?
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  #8  
Old 02-26-2012, 11:53 PM
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Quote:
Originally Posted by ScaleNut
I wonder about the balsa grain on the third model ... is there a benefit to running it that way ?
Maybe so the fin tips don't break off easily? (shrug)

.
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Jay Goemmer
"Centuri Guy"/"Tau Zero"
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Semroc SAM #0029
NAR 86131


"I think about organizing things all the time. Never seems to happen. I find something that piques my interest and I'm off on a quest. Or a Centuri. "

--Bill Eichelberger, 02/22/2022


“Centuri fret buzz in an updated form.”
Bill “Wallyum” Eichelberger re: Estes Flutter-By
03 Sept 2014
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  #9  
Old 02-27-2012, 10:25 AM
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CPMcGraw CPMcGraw is offline
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FWIW...

Look very carefully at the fins from #3, and you should recognize them. Or at least, you have seen the shape used in other designs, twice...

...And not by "Brand C", either...
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  #10  
Old 02-27-2012, 11:01 AM
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Doug Sams Doug Sams is offline
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Quote:
Originally Posted by CenturiGuy
Maybe so the fin tips don't break off easily? (shrug)
I don't see a way to address that without either making the fins 2-piece, or making them from some sort of ply.

As shown in the pic, I agree, that grain orientation does make the outer tabs (tips) more sturdy. But it leaves the inner corners, below the exhaust, susceptible to breaking along the grain lines.

To fix that, the grain should run parallel to the leading edge, but then that would result in the outer tips wanting to snap off. (Push it in here, it pops out there...)

For that shape, with ordinary fin stock, it's a no-win situation. There's gonna be a weak spot. But some paper lamination would probably help. Or maybe make up some home-made balsa ply. Or cut the fins as two pieces glued together such that the grain lines are optimal in both directions.

Doug

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